<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>单例模式</title>
  </head>
  <body>
    <h2>单例模式</h2>

    <button id="loginBtn">登录</button>
    <button id="loginBtn2">登录iframe</button>

    <script src="./index.js"></script>
  </body>
</html>
